The present invention relates to apparatus and methods for protecting against embolization during vascular interventions and improving flow characteristics within a catheter. More particularly, the apparatus and methods of the present invention facilitate blood flow within a catheter by providing a catheter having a radially expandable main body section.
Catheters are commonly manufactured using materials that do not substantially change in cross-sectional area. It is highly desirable that the initial cross-sectional catheter area be relatively small compared to the vasculature for patient comfort and ease of transluminal guidance. However, catheters in which the working diameters remain relatively small have several disadvantages during interventional procedures.
A primary disadvantage of a small cross-sectional catheter area is increased flow resistance within the catheter. A high volume of blood flow being forced through a relatively small lumen may cause damage to blood cells. During interventional procedures involving the removal of emboli, the flow may be further constrained when aspirating large emboli in addition to blood. It therefore would be advantageous to provide a catheter having a small delivery cross-sectional area for transluminal insertion, but which is capable of expanding to a larger cross-sectional area, thus reducing flow resistance within the catheter.
Heretofore, no reliable expandable catheters have been available. U.S. Pat. No. 5,102,401 to Lambert et al. describes a catheter comprising a thermoplastic elastomeric hydrophilic polyurethane coated on at least the outside surface with a hydrophobic polymer. The catheter expands to a larger lumen size in about 3 to 15 minutes when contacted with an aqueous liquid. Additional publications have further discussed catheters which soften upon being raised to a temperature approaching body temperature.
There are several drawbacks associated with such previously known expandable catheters. Such catheters can soften when deployed, resulting in kinking or deformation of the proximal section of the catheter, thereby cutting off flow. Additionally, such catheters require a wait of up to several minutes for the desired expansion to occur. Accordingly, there remains a need for a structurally durable, rapidly expandable catheter.
Previously-known apparatus and methods are known that employ a mechanically expandable occlusive element disposed at the distal end of a catheter. Commonly assigned U.S. Pat. No. 6,206,868 to Parodi discloses an occlusive element comprising a self-expanding wire mesh basket covered with an elastomeric polymer coating. The catheter is initially surrounded by a movable sheath, and is inserted transluminally with the sheath at a distalmost position. The sheath is retracted proximally to cause the basket to deploy, and the basket is again collapsed within the sheath by moving the sheath to its distalmost position.
The occlusive basket described in the Parodi patent is advantageous because it provides a rapidly expandable basket that is substantially flush with the vessel wall to enhance emboli removal. However, emboli then may be funneled into a relatively small cross-sectional area lumen that extends from the site of the stenosis to the vascular entry site. For many procedures, this distance may comprise the vast majority of the overall catheter length. Accordingly, blood flow is potentially constrained throughout the majority of the catheter.
In view of these drawbacks of previously known catheters, it would be desirable to provide apparatus and methods for radially varying the size of a catheter so that the catheter can be maneuvered within the body at a contracted delivery diameter and then self-expands to a larger diameter to facilitate blood flow.
It also would be desirable to provide apparatus and methods for enhancing the flow of blood and emboli within a catheter by expanding the cross-sectional area of the catheter that extends from the site of the stenosis to the vascular entry site.
It still further would be desirable to provide apparatus and methods for rapidly expanding the cross-sectional area of a catheter without relying on chemical or thermal transformations.
It still further would be desirable to provide apparatus and methods for an expandable catheter whereby the structural integrity is not compromised upon expansion.
It still further would be desirable to provide apparatus and methods for efficiently removing emboli by means of an occlusive member that is substantially flush with the vessel wall.
In view of the foregoing, it is an object of the present invention to provide apparatus and methods for radially varying the size of a catheter so that the catheter can be maneuvered within the body at a contracted delivery diameter and then self-expands to a larger diameter in situ to facilitate blood flow.
It is another object of the present invention to provide apparatus and methods for enhancing the flow of blood and emboli within a catheter by expanding the cross-sectional area of the catheter that extends from the site of the stenosis to the vascular entry site.
It is another object of the present invention to provide apparatus and methods for rapidly self-expanding the cross-sectional area of a catheter without relying on chemical or thermal transformations.
It is yet another object of the present invention to provide apparatus and methods for an expandable catheter whereby the structural integrity is not compromised upon expansion.
It is another object of the present invention to provide apparatus and methods for efficiently removing emboli by means of an occlusive member that is substantially flush with the vessel wall.
These and other objects of the present invention are accomplished by providing apparatus and methods suitable for removing emboli and facilitating blood flow within a catheter. The apparatus preferably comprises a catheter having a wire weave configuration, an elastomeric polymer coating covering the weave to provide a blood impermeable membrane, and an outer sheath covering the catheter in a contracted state. The catheter preferably comprises an occlusive distal section, a radially expanding main body, and a fixed diameter proximal section that passes through the vascular entry site.
In a preferred method, the catheter is advanced through the femoral artery and the distal end is positioned proximal to a lesion. As the outer sheath covering the catheter is retracted proximally, the occlusive distal section expands to a predetermined shape to form an occlusive seal against the vessel wall. As the outer sheath is further retracted, the main body of the catheter expands radially to a larger diameter. The outer sheath is further retracted proximally toward the vascular entry site, e.g., the arteriotomy.
The occlusive distal section occludes antegrade flow, and retrograde flow may be induced at the site of the stenosis, e.g., via negative pressure in a venous return line. An interventional procedure, such as angioplasty, stenting or atherectomy, then may be performed to treat the lesion. Emboli generated during the procedure are directed via the retrograde flow into the enlarged lumen of the catheter for subsequent removal.